netdev - Re: Fix NULL dereference in x25

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Message-ID: <20111102021525.GA8512@redhat.com>
Date:	Tue, 1 Nov 2011 22:15:25 -0400
From:	Dave Jones <davej@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org, Matthew Daley <mattjd@...il.com>
Subject: Re: Fix NULL dereference in x25_recvmsg

On Wed, Nov 02, 2011 at 03:10:45AM +0100, Eric Dumazet wrote:
 > Le mardi 01 novembre 2011 à 21:53 -0400, Dave Jones a écrit :
 > > commit cb101ed2 in 3.0 introduced a bug in x25_recvmsg()
 > > When passed bogus junk from userspace, x25->neighbour can be NULL,
 > > as shown in this oops..
 > > 
 > 
 > Your patch seems fine but :
 > 
 > Are you sure this bug is not present on previous kernels ?
 > 
 > It seems we had prior to this commit :
 > 
 > skb_pull(skb, x25->neighbour->extended ?
 > 	X25_EXT_MIN_LEN : X25_STD_MIN_LEN);

It might have been possible with a specifically crafted set of arguments.

It never showed up in testing before now, probably because we were
returning from the function before we got to that skb_pull
via all the other tests that get performed.

	Dave


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